cregit-Linux how code gets into the kernel

Release 4.14 arch/powerpc/platforms/pseries/dtl.c

/*
 * Virtual Processor Dispatch Trace Log
 *
 * (C) Copyright IBM Corporation 2009
 *
 * Author: Jeremy Kerr <jk@ozlabs.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/slab.h>
#include <linux/spinlock.h>
#include <asm/smp.h>
#include <linux/uaccess.h>
#include <asm/firmware.h>
#include <asm/lppaca.h>
#include <asm/debugfs.h>
#include <asm/plpar_wrappers.h>
#include <asm/machdep.h>


struct dtl {
	
struct dtl_entry	*buf;
	
struct dentry		*file;
	
int			cpu;
	
int			buf_entries;
	
u64			last_idx;
	
spinlock_t		lock;
};
static DEFINE_PER_CPU(struct dtl, cpu_dtl);

/*
 * Dispatch trace log event mask:
 * 0x7: 0x1: voluntary virtual processor waits
 *      0x2: time-slice preempts
 *      0x4: virtual partition memory page faults
 */

static u8 dtl_event_mask = 0x7;


/*
 * Size of per-cpu log buffers. Firmware requires that the buffer does
 * not cross a 4k boundary.
 */

static int dtl_buf_entries = N_DISPATCH_LOG;

#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE

struct dtl_ring {
	
u64	write_index;
	
struct dtl_entry *write_ptr;
	
struct dtl_entry *buf;
	
struct dtl_entry *buf_end;
	
u8	saved_dtl_mask;
};

static DEFINE_PER_CPU(struct dtl_ring, dtl_rings);


static atomic_t dtl_count;

/*
 * The cpu accounting code controls the DTL ring buffer, and we get
 * given entries as they are processed.
 */

static void consume_dtle(struct dtl_entry *dtle, u64 index) { struct dtl_ring *dtlr = this_cpu_ptr(&dtl_rings); struct dtl_entry *wp = dtlr->write_ptr; struct lppaca *vpa = local_paca->lppaca_ptr; if (!wp) return; *wp = *dtle; barrier(); /* check for hypervisor ring buffer overflow, ignore this entry if so */ if (index + N_DISPATCH_LOG < be64_to_cpu(vpa->dtl_idx)) return; ++wp; if (wp == dtlr->buf_end) wp = dtlr->buf; dtlr->write_ptr = wp; /* incrementing write_index makes the new entry visible */ smp_wmb(); ++dtlr->write_index; }

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Paul Mackerras9085.71%125.00%
Jeremy Kerr109.52%125.00%
Anton Blanchard32.86%125.00%
Christoph Lameter21.90%125.00%
Total105100.00%4100.00%


static int dtl_start(struct dtl *dtl) { struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu); dtlr->buf = dtl->buf; dtlr->buf_end = dtl->buf + dtl->buf_entries; dtlr->write_index = 0; /* setting write_ptr enables logging into our buffer */ smp_wmb(); dtlr->write_ptr = dtl->buf; /* enable event logging */ dtlr->saved_dtl_mask = lppaca_of(dtl->cpu).dtl_enable_mask; lppaca_of(dtl->cpu).dtl_enable_mask |= dtl_event_mask; dtl_consumer = consume_dtle; atomic_inc(&dtl_count); return 0; }

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Paul Mackerras7977.45%150.00%
Jeremy Kerr2322.55%150.00%
Total102100.00%2100.00%


static void dtl_stop(struct dtl *dtl) { struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu); dtlr->write_ptr = NULL; smp_wmb(); dtlr->buf = NULL; /* restore dtl_enable_mask */ lppaca_of(dtl->cpu).dtl_enable_mask = dtlr->saved_dtl_mask; if (atomic_dec_and_test(&dtl_count)) dtl_consumer = NULL; }

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Paul Mackerras6394.03%150.00%
Jeremy Kerr45.97%150.00%
Total67100.00%2100.00%


static u64 dtl_current_index(struct dtl *dtl) { return per_cpu(dtl_rings, dtl->cpu).write_index; }

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Paul Mackerras1460.87%150.00%
Jeremy Kerr939.13%150.00%
Total23100.00%2100.00%

#else /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
static int dtl_start(struct dtl *dtl) { unsigned long addr; int ret, hwcpu; /* Register our dtl buffer with the hypervisor. The HV expects the * buffer size to be passed in the second word of the buffer */ ((u32 *)dtl->buf)[1] = DISPATCH_LOG_BYTES; hwcpu = get_hard_smp_processor_id(dtl->cpu); addr = __pa(dtl->buf); ret = register_dtl(hwcpu, addr); if (ret) { printk(KERN_WARNING "%s: DTL registration for cpu %d (hw %d) " "failed with %d\n", __func__, dtl->cpu, hwcpu, ret); return -EIO; } /* set our initial buffer indices */ lppaca_of(dtl->cpu).dtl_idx = 0; /* ensure that our updates to the lppaca fields have occurred before * we actually enable the logging */ smp_wmb(); /* enable event logging */ lppaca_of(dtl->cpu).dtl_enable_mask = dtl_event_mask; return 0; }

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Paul Mackerras7662.81%133.33%
Jeremy Kerr4436.36%133.33%
Nishanth Aravamudan10.83%133.33%
Total121100.00%3100.00%


static void dtl_stop(struct dtl *dtl) { int hwcpu = get_hard_smp_processor_id(dtl->cpu); lppaca_of(dtl->cpu).dtl_enable_mask = 0x0; unregister_dtl(hwcpu); }

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Paul Mackerras37100.00%1100.00%
Total37100.00%1100.00%


static u64 dtl_current_index(struct dtl *dtl) { return lppaca_of(dtl->cpu).dtl_idx; }

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Paul Mackerras21100.00%1100.00%
Total21100.00%1100.00%

#endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
static int dtl_enable(struct dtl *dtl) { long int n_entries; long int rc; struct dtl_entry *buf = NULL; if (!dtl_cache) return -ENOMEM; /* only allow one reader */ if (dtl->buf) return -EBUSY; n_entries = dtl_buf_entries; buf = kmem_cache_alloc_node(dtl_cache, GFP_KERNEL, cpu_to_node(dtl->cpu)); if (!buf) { printk(KERN_WARNING "%s: buffer alloc failed for cpu %d\n", __func__, dtl->cpu); return -ENOMEM; } spin_lock(&dtl->lock); rc = -EBUSY; if (!dtl->buf) { /* store the original allocation size for use during read */ dtl->buf_entries = n_entries; dtl->buf = buf; dtl->last_idx = 0; rc = dtl_start(dtl); if (rc) dtl->buf = NULL; } spin_unlock(&dtl->lock); if (rc) kmem_cache_free(dtl_cache, buf); return rc; }

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Paul Mackerras12171.60%240.00%
Jeremy Kerr3420.12%240.00%
Nishanth Aravamudan148.28%120.00%
Total169100.00%5100.00%


static void dtl_disable(struct dtl *dtl) { spin_lock(&dtl->lock); dtl_stop(dtl); kmem_cache_free(dtl_cache, dtl->buf); dtl->buf = NULL; dtl->buf_entries = 0; spin_unlock(&dtl->lock); }

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Jeremy Kerr3667.92%125.00%
Paul Mackerras1426.42%250.00%
Nishanth Aravamudan35.66%125.00%
Total53100.00%4100.00%

/* file interface */
static int dtl_file_open(struct inode *inode, struct file *filp) { struct dtl *dtl = inode->i_private; int rc; rc = dtl_enable(dtl); if (rc) return rc; filp->private_data = dtl; return 0; }

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Jeremy Kerr51100.00%1100.00%
Total51100.00%1100.00%


static int dtl_file_release(struct inode *inode, struct file *filp) { struct dtl *dtl = inode->i_private; dtl_disable(dtl); return 0; }

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Jeremy Kerr33100.00%1100.00%
Total33100.00%1100.00%


static ssize_t dtl_file_read(struct file *filp, char __user *buf, size_t len, loff_t *pos) { long int rc, n_read, n_req, read_size; struct dtl *dtl; u64 cur_idx, last_idx, i; if ((len % sizeof(struct dtl_entry)) != 0) return -EINVAL; dtl = filp->private_data; /* requested number of entries to read */ n_req = len / sizeof(struct dtl_entry); /* actual number of entries read */ n_read = 0; spin_lock(&dtl->lock); cur_idx = dtl_current_index(dtl); last_idx = dtl->last_idx; if (last_idx + dtl->buf_entries <= cur_idx) last_idx = cur_idx - dtl->buf_entries + 1; if (last_idx + n_req > cur_idx) n_req = cur_idx - last_idx; if (n_req > 0) dtl->last_idx = last_idx + n_req; spin_unlock(&dtl->lock); if (n_req <= 0) return 0; i = last_idx % dtl->buf_entries; /* read the tail of the buffer if we've wrapped */ if (i + n_req > dtl->buf_entries) { read_size = dtl->buf_entries - i; rc = copy_to_user(buf, &dtl->buf[i], read_size * sizeof(struct dtl_entry)); if (rc) return -EFAULT; i = 0; n_req -= read_size; n_read += read_size; buf += read_size * sizeof(struct dtl_entry); } /* .. and now the head */ rc = copy_to_user(buf, &dtl->buf[i], n_req * sizeof(struct dtl_entry)); if (rc) return -EFAULT; n_read += n_req; return n_read * sizeof(struct dtl_entry); }

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Jeremy Kerr21371.48%133.33%
Paul Mackerras8528.52%266.67%
Total298100.00%3100.00%

static const struct file_operations dtl_fops = { .open = dtl_file_open, .release = dtl_file_release, .read = dtl_file_read, .llseek = no_llseek, }; static struct dentry *dtl_dir;
static int dtl_setup_file(struct dtl *dtl) { char name[10]; sprintf(name, "cpu-%d", dtl->cpu); dtl->file = debugfs_create_file(name, 0400, dtl_dir, dtl, &dtl_fops); if (!dtl->file) return -ENOMEM; return 0; }

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Jeremy Kerr60100.00%1100.00%
Total60100.00%1100.00%


static int dtl_init(void) { struct dentry *event_mask_file, *buf_entries_file; int rc, i; if (!firmware_has_feature(FW_FEATURE_SPLPAR)) return -ENODEV; /* set up common debugfs structure */ rc = -ENOMEM; dtl_dir = debugfs_create_dir("dtl", powerpc_debugfs_root); if (!dtl_dir) { printk(KERN_WARNING "%s: can't create dtl root dir\n", __func__); goto err; } event_mask_file = debugfs_create_x8("dtl_event_mask", 0600, dtl_dir, &dtl_event_mask); buf_entries_file = debugfs_create_u32("dtl_buf_entries", 0400, dtl_dir, &dtl_buf_entries); if (!event_mask_file || !buf_entries_file) { printk(KERN_WARNING "%s: can't create dtl files\n", __func__); goto err_remove_dir; } /* set up the per-cpu log structures */ for_each_possible_cpu(i) { struct dtl *dtl = &per_cpu(cpu_dtl, i); spin_lock_init(&dtl->lock); dtl->cpu = i; rc = dtl_setup_file(dtl); if (rc) goto err_remove_dir; } return 0; err_remove_dir: debugfs_remove_recursive(dtl_dir); err: return rc; }

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Jeremy Kerr16894.38%125.00%
Paul Mackerras84.49%125.00%
Nishanth Aravamudan10.56%125.00%
Tejun Heo10.56%125.00%
Total178100.00%4100.00%

machine_arch_initcall(pseries, dtl_init);

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Jeremy Kerr77752.25%211.11%
Paul Mackerras66244.52%316.67%
Nishanth Aravamudan211.41%15.56%
Michael Ellerman70.47%211.11%
Tejun Heo50.34%211.11%
Frédéric Weisbecker30.20%15.56%
Anton Blanchard30.20%15.56%
David Howells20.13%15.56%
Sachin P. Sant20.13%15.56%
Christoph Lameter20.13%15.56%
Alexey Dobriyan10.07%15.56%
Deepthi Dharwar10.07%15.56%
Linus Torvalds10.07%15.56%
Total1487100.00%18100.00%
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